At a glance

100-word definitions of frequently used terms in Cardiac Research

Cardiology

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Angina Pectoris. Angina pectoris is the result of myocardial ischemia caused by an imbalance between myocardial blood supply and oxygen demand. Angina is a common presenting symptom (typically, chest pain) among patients with coronary artery disease. When pain lasts longer than 5 minutes and is not relieved by rest, angina pectoris derives to infarction and restoration of the blood supply is not enough to avoid tissue damage.. Atherosclerosis is the most common cause of epicardial coronary artery stenosis and, hence, angina pectoris. Risk factors include family history, smoking, diabetes mellitus,metabolic syndrome, hyperlipidaemia, hypertension, obesity and lack of exercise.

Aorta. The aorta is the largest artery in the body, originating from the left ventricle and extending down to the abdomen, where it branches off into the common iliac arteries. The aorta distributes oxygenated blood to all parts of the body through the systemic circulation. It is divided into four segments: ascending aorta, arch of aorta, thoracic aorta and abdominal aorta. The aorta consists of a heterogeneous mixture of smooth muscle, nerves, intimal cells, endothelial cells, fibroblast-like cells, and a complex extracellular matrix. The vascular wall consists of several layers known as the tunica adventitia, tunica media, and tunica intima.

Atherosclerosis. Atherosclerosis is a type of arteriosclerosis. It is a process of progressive thickening and hardening of the walls of medium-sized and large arteries resulting from deposition of atheromatous plaques containing cholesterol and lipids on the innermost arterial layers. Atherosclerosis is responsible for much coronary artery disease and many strokes. Apolipoprotein E is important for removing excess cholesterol from the blood by carrying cholesterol to receptors on the surface of liver cells. Defects in this protein increase the risk of atherosclerosis. Most common risk factors include high levels of cholesterol, hypertension, smoking, diabetes and a genetic family history of atherosclerotic disease.

Atrial fibrilation. Atrial fibrillation (AF) is the most common cardiac arrhythmia and involves the two upper chambers (atria) of the heart. It is caused by multiple reentrant waveforms within the atria, which bombard the atrioventricular node, commonly leading to a tachycardia that is irregularly irregular. Blood is not pumped completely out of the atria, and therefore it may pool and clot, resulting in stroke if clot leaves the heart and becomes lodged in an artery in the brain. Risk factors for AF include age, male sex, hypertension, valvular heart disease, left ventricular hypertrophy, coronary artery disease, diabetes mellitus, smoking and any form of carditis.

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Beta blockers. Beta blockers are competitive antagonists that block the receptor sites for epinephrine (adrenaline) and norepinephrine (noradrenaline). These receptors (beta receptors) are found on cells of cardiac muscles, smooth muscles, airways, arteries, kidneys, and other tissues that are part of the sympathetic nervous system and lead to stress responses. Beta blockers are particularly used as drugs to manage cardiac arrhythmias, and to protect the heart from a second heart attack after a first attack. The first clinically significant beta blockers were synthesized by Sir James W. Black in 1964.

Bicuspid aortic valve. The aortic valve is a one-way valve between the
heart and the aorta. Normally, the aortic valve has three small leaflets that
open widely with every ventricular systole allowing for the blood to flow from
the left ventricle. During diastole, the valve closes to prevent blood from
flowing backwards into the heart. Bicuspid aortic valves (BAV) have only two
leaflets and therefor do not function perfectly. BAV is the most common
congenital heart defect, with a prevalence of 1-2%. In this patients, the
aortic valve may function adequately for years without causing symptoms.

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Diastole. The diastole is the period of time when the heart fills with blood after systole (contraction). At the same time, there is a corresponding decrease in arterial blood pressure to its minimum (diastolic blood pressure), normally about 80 millimetres of mercury in humans. Atrial diastole is the period during which the atria are relaxing after atrial systole.

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Electrocardiogram. ECG or EKG is a diagnostic tool that measures and records the electrical activity of the heart, allowing diagnosis of a wide range of heart conditions. Although first introduced by Einthoven in 1893, the standard 12-lead ECG arrived in 1942. The atria make the first wave called a “P wave", following a flat line when the electrical impulse goes to the bottom chambers. The right and left ventricles make the next wave called a “QRS complex." The final “T wave” represents the return to rest for the ventricles. ECG is a recording tool; it doesn’t send electricity into the body.

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Hypertension. Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. Below 80 mmHg for systolic pressure and 120 mmHg for diastolic are generally considered as normal levels. Persistent hypertension is one of the risk factors for stroke, myocardial infarction, heart failure and arterial aneurysm, and is a leading cause of chronic kidney failure. Amongst the most prevalent risk factors appear being overweight, smoking, little or no exercise, high salt diets, high alcohol consumption, stress, ethnic background and a history of high blood pressure in the family.

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Marfan syndrome. Marfan syndrome is a congenital disease resulting from mutations in the fibrillin-1 gene, on human chromosome 15. The protein encoded by this gene is a major building block of microfibrils in connective tissues. In the cardiovascular system, abnormalities involving microfibrils weaken the aortic wall, and progressive aortic dilatation and eventual aortic dissection occur because of tension caused by left ventricular ejection impulses. A panel of pleiotropic manifestations is associated to this mutation, being one of the most common single-gene malformation syndromes. Its inheritance is dominant, although approximately 25% of the cases are due to de novo mutations.

Mitral valve. The mitral valve (also bicuspid valve or left atrioventricular valve) is a dual-flap valve in the heart that lies between the left atrium and the left ventricle. It has two leaflets (the anteromedial leaflet and the posterolateral leaflet) that guard the opening. These valve leaflets are prevented from prolapsing into the left atrium by the action of tendons attached to the posterior surface of the valve, the chordae tendineae. These tendons are attached at one end to the papillary muscles and the other to the valve cusps. The opening is surrounded by a fibrous ring known as the mitral valve annulus.

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Stroke. A stroke is a rapidly developing loss of brain function due to disturbance in the blood supply to the brain due to ischemia or a hemorrhage. The affected area of the brain is unable to function, leading to inability to move one or more limbs on one side of the body, inability to understand or formulate speech, or an inability to see one side of the visual field. Hemorrhagic strokes have a much higher death rate than ischemic strokes. Risk factors are diabetes, cholesterolemia, hypertension, heart disease or atrial fibrillation, overweight, excessive alcohol consumption, physical inactivity, smoking, stress and family history.

Sinoatrial node. The sinoatrial node (SAN) is a group of cells on the right atrium wall, near the entrance of the superior vena cava. It acts as the impulse-generating tissue that generates the normal sinus rhythm. Cells on SAN are modified non-contractile cardiomyocytes. Since they generate action potentials slightly faster than other areas with pacemaker potential, it normally initiates electrical impulse, overcoming regions such as the atrioventricular node or Purkinje fibers. The SAN is inervated by sympathetic and parasympathetic nerves and it is also susceptible of hormonal regulation. However, it generates intrinsec potential actions for a heart rate as 60-100 beats/min.

Systole. Period of contraction of the heart ventricles that occurs between the first and second heart sounds. Systole causes the ejection of blood into the aorta and pulmonary trunk. Lasting usually 0.3 to 0.4 second, ventricular systole is introduced by a very brief period of contraction, followed by the ejection phase, during which 80 to 100cc of blood leave each ventricle. During systole, arterial blood pressure reaches its peak (systolic blood pressure), normally about 120 millimetres of mercury in human beings. Atrial systole represents the contraction of myocardium of the left and right atria and it occurs late in ventricular diastole.

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Tricuspid valve. The tricuspid valve is on the right dorsal side of the mammalian heart, between the right atrium and the right ventricle and it regulates the blood flow between these heart chambers. The normal tricuspid valve usually has three leaflets and three papillary muscles but may also occur with two or four leaflets; the number may change during life. They are connected to the papillary muscles by the chordae tendineae, which lie in the right ventricle.

Troponin test. When heart muscle is damaged, as in a myocardial infarction, cardiac troponins T and I leak out of cells into the bloodstream. Troponin levels rise within 4-6 hours after the beginning of chest pain or heart damage, and they stay elevated for at least one week. This allows detection of a myocardial infarction occurred days earlier. Generally, troponin levels above 2.0 ng/mL indicate a significant myocardial injury and an increased risk for future events. Levels between 0.5 and 2.0 ng/mL indicate a diagnosis of unstable angina, other heart disorders, or chronic kidney failure.

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General Research

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Flow cytometry. Flow cytometry is a technique for counting and examining microscopic particles, such as cells by suspending them in a stream of fluid and passing them by an electronic detection apparatus based on a laser beam. An absorbance or fluorescence profile of the sample is produced. Using antibody-based labeling, flow cytometry is routinely used in the diagnosis of health disorders, especially blood cancers, but has many other applications in both research and clinical practice. Flow cytometry can be used with automated sorting devices to sort successive droplets of the stream into different fractions depending on the fluorescence emitted by each droplet.

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PCR.

Polymerase Chain Reaction is a molecular technique which allows the production of large quantities of a specific DNA sequence from a DNA template using a simple enzymatic reaction without a living organism. It bases on heat and cold cycles controlling enzymatic activity and cleavage of polymerase. Reaction is performed on an automated cycler, a device which rapidly heats and cools the test tubes containing the reaction mixture and allows increase exponentially the number of copies from a few template molecules. Since its introduction on the 80’s, PCR has become an invaluable research technique as well as an accurate diagnostic tool.

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Stem cells.

Stem cells are cells from multicellular organisms characterized by the ability to renew themselves through mitotic cell division and differentiate into a diverse range of specialized cell types. Stem cells exist form embryonic and adult origin. While self renewal defines the stem cell status, different degrees of potentiality are found between totipotent, pluripotent, multipotent, oligopotent and unipotent stem cells. Different uses have been proposed for them including the injection of stem cells from diverse origins on the infracted myocardium, a therapy which became popular on early 2000s. However, sources and features of injected cells are currently being reviewed.

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Western Blot.

The Western blot is a widely used analytical technique used to detect specific proteins in a given homogenate or extract (from cells or tissues). It uses gel electrophoresis to separate native or denatured proteins by the length of the polypeptide chain (denaturing) or by the 3D structure of the protein (native). The proteins are then transferred to a membrane (typically nitrocellulose or PVDF, which have avidity for protein binding), where they are probed using antibodies specific to the target protein or protein substructure.